Light-emitting diodes (LEDs) have been changing the way we see the world since the 1960s. Their usage in everyday life is pervasive and continues to increase thanks to the cutting-edge research being done in the field of optics.
To highlight breakthroughs in LEDs, the editors of Energy Express, a bi-monthly supplement to Optics Express, the open-access journal of the Optical Society (OSA), today published a special Focus Issue on Optics in LEDs for Lighting. The issue is organized and edited by Guest Editors Jae-Hyun Ryou and Russell Dupuis of the Georgia Institute of Technology.
"The papers in this Focus Issue represent the outcome of state-of-the-art research and development by recognized experts in the field of LEDs, said Ryou. "These latest advances are truly exceptional and will prove to be invaluable to advancements in lighting technology."
LEDs continue to prove themselves as the future in lighting, with applications in everything from vehicle headlights to stadium displays to video cameras. In addition to their current commercial applications, LEDs have opened up an era of solid-state lighting (SSL) with capabilities of emitting photons of either primary colors or white light. With their continuous improvements in luminous efficiency compared with conventional light sources, LEDs will lead to significant energy savings when used as a ubiquitous light source for general lighting applications. The papers in this Focus Issue feature state-of-the-art research and development that address the technical challenges and possible solutions for visible LEDs to be widely used in SSL, while also focusing on the major challenges associated with improving luminous efficiency and simultaneously delivering superb color quality at a reasonable cost.
Key Findings & Select Papers
The following papers are some of the highlights of the Energy Express Focus Issue on Optics in LEDs for Lighting. All are included in Volume 20, issue S4 and can be accessed online at http://www.opticsinfobase.org/ee.
Typical III-N-based visible LED structures are grown on sapphire substrates; however, a possible way to lower the capital cost of LED-based SSL technologies is to fabricate the devices on silicon substrates. Kei May Lau, et al. report blue-emitting LEDs on silicon substrates to lower the manufacturing cost of visible LEDs. The paper addresses many important technical issues associated with LEDs on silicon substrates, such as strain management and crack-formation in the epitaxial structure, thermal management of the chips, and external quantum efficiency of the devices including light extraction. pp. A956 http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-104-A956
It is believed that current and future SSL is based on LEDs and phosphors. Jeff Tsao and Jonathan Wierer, et al. challenge this common belief that the narrow spectral linewidth and the high capital cost of lasers makes them unsuited for general illumination purposes. They discuss the use of lasers for higher power and efficiency at high current densities for SSL and experimentally demonstrate that four-color (RYGB) laser white illuminant is virtually indistinguishable from high quality state-of-the-art white reference illuminants. This result suggests that lasers can also be a serious contender for solid-state lighting in some applications. pp. A982 http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-104-A982
In order to improve extraction efficiency, hence external quantum efficiency, of LED devices, photons generated in the active region should escape out of the naturally formed slab waveguide structure formed by the LEDs' epitaxial layers. A paper by Seong-Ju Park, et al. demonstrates that tungsten metal can be used not only as a mask for epitaxial lateral overgrowth but also for the formation of an air void underneath it to improve both internal quantum efficiency and extraction efficiency of the LEDs. Whereas several similar approaches have been demonstrated, this study is unique in the formation of an air void as an optical scatterer without resorting to a complicated etching process. pp. A943 http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-104-A943
For the improvement of internal quantum efficiency, C. C. Yang and Yean-Woei Kiang, et al. investigate surface plasmon coupling with radiating dipoles (electron-hole pairs) experimentally and theoretically. The team demonstrates improvement in the efficiency droop, a term commonly used by the LED community to refer to the reduction in emission efficiency with increasing injection current, as well as in internal quantum efficiency. They also numerically study the effects of coupling based on a coupling model between a radiating dipole and the localized surface plasmon induced by Ag nanoparticles. pp. A914 http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-104-A914
About Energy Express
As a special bi-monthly supplement to Optics Express, Energy Express is dedicated to rapidly communicating new developments in optics for sustainable energy. Energy Express will have original research side-by-side with review articles written by the world's leading experts in the science and engineering of light and its impact on sustainable energy development, the environment, and green technologies. For more information, see: http://www.OpticsInfoBase.org/EE.
About Optics Express
Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by the Optical Society and edited by C. Martijn de Sterke of the University of Sydney. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/OE.
Uniting more than 106,000 professionals from 134 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.
Lyndsay Basista | EurekAlert!
Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University
TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences